SRC/zgeqrfp.f(3)           Library Functions Manual           SRC/zgeqrfp.f(3)

NAME
       SRC/zgeqrfp.f

SYNOPSIS
   Functions/Subroutines
       subroutine zgeqrfp (m, n, a, lda, tau, work, lwork, info)
           ZGEQRFP

Function/Subroutine Documentation
   subroutine zgeqrfp (integer m, integer n, complex*16, dimension( lda, * )
       a, integer lda, complex*16, dimension( * ) tau, complex*16, dimension(
       * ) work, integer lwork, integer info)
       ZGEQRFP

       Purpose:


           !>
           !> ZGEQR2P computes a QR factorization of a complex M-by-N matrix A:
           !>
           !>    A = Q * ( R ),
           !>            ( 0 )
           !>
           !> where:
           !>
           !>    Q is a M-by-M orthogonal matrix;
           !>    R is an upper-triangular N-by-N matrix with nonnegative diagonal
           !>    entries;
           !>    0 is a (M-N)-by-N zero matrix, if M > N.
           !>
           !>

       Parameters
           M

           !>          M is INTEGER
           !>          The number of rows of the matrix A.  M >= 0.
           !>

           N

           !>          N is INTEGER
           !>          The number of columns of the matrix A.  N >= 0.
           !>

           A

           !>          A is COMPLEX*16 array, dimension (LDA,N)
           !>          On entry, the M-by-N matrix A.
           !>          On exit, the elements on and above the diagonal of the array
           !>          contain the min(M,N)-by-N upper trapezoidal matrix R (R is
           !>          upper triangular if m >= n). The diagonal entries of R
           !>          are real and nonnegative; The elements below the diagonal,
           !>          with the array TAU, represent the unitary matrix Q as a
           !>          product of min(m,n) elementary reflectors (see Further
           !>          Details).
           !>

           LDA

           !>          LDA is INTEGER
           !>          The leading dimension of the array A.  LDA >= max(1,M).
           !>

           TAU

           !>          TAU is COMPLEX*16 array, dimension (min(M,N))
           !>          The scalar factors of the elementary reflectors (see Further
           !>          Details).
           !>

           WORK

           !>          WORK is COMPLEX*16 array, dimension (MAX(1,LWORK))
           !>          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
           !>

           LWORK

           !>          LWORK is INTEGER
           !>          The dimension of the array WORK.
           !>          LWORK >= 1, if MIN(M,N) = 0, and LWORK >= N, otherwise.
           !>          For optimum performance LWORK >= N*NB, where NB is
           !>          the optimal blocksize.
           !>
           !>          If LWORK = -1, then a workspace query is assumed; the routine
           !>          only calculates the optimal size of the WORK array, returns
           !>          this value as the first entry of the WORK array, and no error
           !>          message related to LWORK is issued by XERBLA.
           !>

           INFO

           !>          INFO is INTEGER
           !>          = 0:  successful exit
           !>          < 0:  if INFO = -i, the i-th argument had an illegal value
           !>

       Author
           Univ. of Tennessee


           Univ. of California Berkeley


           Univ. of Colorado Denver


           NAG Ltd.

       Further Details:


           !>
           !>  The matrix Q is represented as a product of elementary reflectors
           !>
           !>     Q = H(1) H(2) . . . H(k), where k = min(m,n).
           !>
           !>  Each H(i) has the form
           !>
           !>     H(i) = I - tau * v * v**H
           !>
           !>  where tau is a complex scalar, and v is a complex vector with
           !>  v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i),
           !>  and tau in TAU(i).
           !>
           !> See Lapack Working Note 203 for details
           !>

       Definition at line 149 of file zgeqrfp.f.

Author
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LAPACK                          Version 3.12.0                SRC/zgeqrfp.f(3)